JPH0266783A - Head moving speed controller for rotary recorder - Google Patents

Abstract

PURPOSE:To improve the resolution of a D/A converter by setting the input/ output characteristics of the D/A converter so that the rate of an output change with respect to an input change may be decreased when an aimed speed is slow, and it may be increased when the aimed speed is fast. CONSTITUTION:A D/A converter 8 generates a current iC21 obtained by multiplying 1/256 current values of a reference current iB17 supplied to a reference current input terminal 10 by eight-bit input data to an output terminal 11, and when a feedback resistance RD23 is connected from an aimed speed voltage output VO13 converted into a voltage by an operating amplifier 12 to a reference current input terminal 10, and when a current iD24 is supplied, the relation between the input data and the output voltage is made into a hyperbolic function passing through an origin. By suitably setting the value of the feedback resistance RD23 with the use of it, a nonlinear D/A converter 8, which raises the output resolution when the input data are small and gradually lowers the resolution as the input data become larger, can be obtained, and the head speed control at high accuracy is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head movement speed control device for a recording device (rotary recording device) using a rotating 8J medium such as a magnetic disk device, and in particular, The present invention relates to a head movement speed control device for a rotary recording device that can improve the accuracy of a speed control system for moving the head.

[Conventional technology]

Conventionally, as a head movement speed control circuit for this type of magnetic disk device, as shown in Japanese Patent Laid-Open No. 55-22207 and Japanese Patent Laid-open No. 55-45132, the target speed of the head stored as digital data is controlled. A device equipped with a D/A converter for converting an analog signal to a target speed is known, but this D/A converter cannot obtain an analog output proportional to the digital value input manually to the D/A converter. It is a premise.

[Problem to be solved by the invention]

As magnetic disk drives become more water-tight and access faster, speed control during head movement and positioning is required to be more precise. A much smaller value is now required compared to . This trend is
This becomes especially noticeable when the track width is narrowed.
As a result, the resolution of the D/A converter has become insufficient. A common way to improve the resolution of a D/A converter is to increase the number of conversion bits of the D/A converter (for example, from 8 bits to 12 bits), but generally speaking, the control microcomputer that controls the target speed is 8
However, outputting 12 bit data increases the time constraints for high-speed access. Further, D/A converters of 8 bits or more have problems in that they are expensive and have large external dimensions, which is disadvantageous in terms of miniaturization of the device.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to improve resolution in a head movement speed control device for a rotary recording device by using a D/A converter having the same number of conversion bits as the conventional device. The objective is to improve the precision of head speed control for high-density tracks.

[Failure to solve the problem]

In order to achieve the above object, a head movement speed control device for a rotary recording device according to the present invention includes a target speed storage section that stores a preset target speed, and a digital target speed signal obtained from the storage section that stores a preset target speed. It has a D/A converter that converts the signal into a signal, and a control means that controls the head to move along the target speed based on the output of the head movement speed detector and the analog signal.
The input/output characteristics of the converter are configured to have nonlinear characteristics such that the ratio of output change to input change is small when the target speed is low, and this ratio increases as the target speed becomes higher.

For example, this input/output characteristic can be a hyperbolic function.

The nonlinear (hyperbolic function) input/output characteristic of the D/A converter is obtained by feeding back the output voltage of the D/A converter to the reference current of the D/A converter.

[Effect]

The operation based on the above configuration will be explained.

A general D/A converter has a reference current input terminal, and when the digital input value is maximum, for example 255 for 8-bit data, the output terminal outputs approximately the same amount of current as the reference current. , the human data is N (N
=0.1,2. ..., 255), a current N/256 times the reference current is output. When using a voltage value as an output value, a current/voltage conversion circuit is added to the output current.

When a feedback loop is constructed by connecting the output voltage and the reference current input terminal via a resistor in the D/A converter as described above, the relationship between the human power data and the output voltage becomes a hyperbolic function passing through the origin. By using this and appropriately setting the value of the feedback resistance, the output resolution will be higher when the human input data is smaller (i.e., the target speed is lower), and the input data will be larger (i.e., the target speed will be higher). ), it is possible to obtain a nonlinear D/A converter whose resolution gradually decreases.

Therefore, in head speed control, the target speed output becomes smaller as the head approaches the target track, but at the same time the resolution improves and highly accurate head speed control becomes possible. On the other hand, at high speeds, the output resolution of the target speed is reduced, but since the output value itself is large, the error rate is small and the influence is small.

It should be noted that nonlinear characteristics similar to those described above can be realized by using a logarithmic amplifier (logamp), but stability and
It is difficult to obtain one with excellent accuracy and characteristics. On the other hand, when using the D/A converter according to the present invention, the desired characteristics with excellent stability and precision can be achieved with a simple configuration simply by adding feedback means such as a resistor to a normal D/A converter. You can get what you want.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. A servo head 1 is used to read servo information recorded on a servo disk, and the read signal is amplified by a servo amplifier 2. The position detector 3 is a detector that reproduces a head position signal from a search signal. The speed detector 4 is for reproducing the head speed signal from the position signal, and the track passage detector 5 is for detecting that the head has passed the track based on the position signal, and the passing signal is sent to the microcomputer. is input.

Various target speed curves are stored as digital data in a storage unit such as a ROM (not shown) in the microcomputer 6, and the microcomputer 6 stores one target speed curve in order to move the head to a target track. A target speed digital output cuff corresponding to the curve is output from this storage section to the D/A converter 8. D/
The A converter 8 has an 8-hit digital input terminal 9 and a reference current input terminal 10, and a current that is 1/256 of the current flowing into the reference current input terminal multiplied by the 8-hit input data is generated at the output terminal 11. It works like that.

The operational amplifier 12 is used to convert the output current of the D/A controller 8 into a voltage. The target speed voltage output 13 obtained here and the speed signal obtained from the speed detector 4 are subtracted by the error amplifier 14, and the speed deviation signal is input to the actuator drive circuit 15 to drive the servo head 1 and data head. The actuator 16 for movement is driven.

Next, the operation of the D/A converter will be explained in more detail. The D/A converter 8 generates at the output terminal 11 a current obtained by multiplying the input data N based on the reference current 1B17, and generally has a reference power supply 18 and generates a basic reference current determined by the reference current control resistor RA19. Enter tA2
0 is used to determine the reference current 1f117. In this case, input data and output current t.

21 is a proportional relationship and is the target speed output voltage V. 13 is expressed as follows, where N is the input data.

Feedback resistance R0 is applied to the reference current input terminal 10 from the target speed output voltage 13 for the circuit in the above configuration.
By connecting 23, the D/A converter circuit described above can have nonlinear characteristics. The potential of the reference current input terminal 10 is always a constant potential, and if it is Ov,
The current flowing through the feedback resistor R923 is in
24, input data N and output ■. The following relational expression holds true between them, and when rearranged, Equation (5) can be expressed as follows, and the input-output relationship becomes a hyperbolic function passing through the origin.

This relationship is shown in FIG. The horizontal axis 25 represents human power data, and the vertical axis 2G represents target speed output voltage. The wavy line 27 indicates α-〇, that is, the input-output relationship in the absence of the feedback resistor R923, which is a straight line, indicating that the input-output is proportional. The solid line 28 indicates α=0.5. That is, this is the case where RD=2XRC. The output change per 1 bit of input data is obtained by differentiating equation (6), and in the case of α-0,5, the resolution when the input data N is around O is 4 times the resolution when N = 256, which is slow. It can be seen that it is possible to finely change the target speed over time.

However, when the D/A converter is made nonlinear in this way, the target speed data generated by the microcomputer must be processed in advance so that the output of the D/A converter is at the same level as before the nonlinearity. It is.

According to this embodiment, by simply adding one feedback resistor Rn to the conventional D/A converter circuit, it is possible to obtain the desired nonlinear characteristic of a hyperbolic function.

Note that the input/output characteristics are not limited to hyperbolic functions, but may also be other nonlinear curves.

〔Effect of the invention〕

As explained in detail above, according to the head movement speed control device for a rotary recording device of the present invention, the input/output characteristics of the D/A converter that converts a digital target speed signal into an analog target speed signal are By the way, the ratio of output change to input change is made low, and this ratio increases as the target speed increases, so that when the head speed is low, there is no need to use a larger I/A converter. The output resolution of the D/A converter can be improved, and as a result, highly accurate head speed control can be achieved using an inexpensive /A converter. In addition, since there is no need to increase the number of bits of the target speed digital data output from the microcomputer, there is no increase in processing time, which is a problem during high-speed movement, and the head movement can be made faster and the track pitch narrower. , has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a head movement speed control system of a magnetic disk drive according to an embodiment of the present invention, and FIG. 2 is a diagram showing input/output characteristics of a nonlinear D/A converter according to the present invention. 1... Servo head, 2... Servo amplifier, 3... Position detector, 4... Speed detector, 5... Truck Passage detector, 6...
...Microcomputer, 7...Target speed digital output, 8...D/A converter, 9
......Digital input terminal, 10...Reference current input terminal, 11...Output terminal, 12...
...Operation amplifier, 13...Target speed voltage output, 14...Error amplifier, 15...
Actuator drive circuit, 16... Actuator, 17... Reference current 1B, 18...
...Reference power supply: V, , 19...Reference current control resistor RA, 20...Basic reference current = iA, 2
1... Output current: Io, 22... Current-voltage conversion resistance: Rc, 23... Feedback resistance: R,, 24... Feedback current near D I

Claims (1)

[Claims] 1. A head for recording or reproducing tracks on a rotary recording medium, a detector for detecting the moving speed of the head, and a target for moving the head to a target track. a target speed storage unit that presets and stores a speed; a D/A converter that converts a digital target speed signal obtained from the target speed storage unit into an analog signal;
In a head movement speed control device for a rotary recording device, the head movement speed control device includes a control means for controlling the head to move along the target speed using the output of the detector and the analog signal, the D/A converter comprising: , a rotary type characterized in that the target speed is nonlinearly converted so that the ratio of output change to input change is small when the target speed is relatively low, and this ratio increases as the target speed increases. A head movement speed control device for a recording device. 2. The head movement speed control device for a rotary recording device according to claim 1, wherein the D/A converter is configured so that an input-to-output characteristic is given by a hyperbolic function.